import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.SocketException;

public class EchoServer {
    private DatagramSocket socket = null;
    public EchoServer(int port) throws SocketException {
        socket = new DatagramSocket(port);
    }
    public void start() throws IOException {
        System.out.println("服务器启动");
        while(true){
            DatagramPacket requestPacket = new DatagramPacket(new byte[4096],4096);
            socket.receive(requestPacket);
            String request = new String(requestPacket.getData(),0,requestPacket.getLength());
            String response = process(request);
            DatagramPacket responsePacket = new DatagramPacket(response.getBytes(),response.getBytes().length,
                    requestPacket.getSocketAddress());
            socket.send(responsePacket);
            System.out.printf("%s : %d req : %s,resp:%s\n",requestPacket.getAddress().toString(),
                    requestPacket.getPort(),request,response);
        }
    }

    public String process(String request) {
        return request;
    }

    public static void main(String[] args) throws IOException {
        EchoServer server = new EchoServer(9090);
        server.start();
    }
}
